The United States international scored just once in 28 games for Hull City during the 2009-10 season as the Tigers were relegated from the top flight.
However, the 23-year-old found the net on a regular basis during his time at AZ Alkmaar and scored 31 goals last season.
"I think I just became a better player in Holland than the one when I was at Hull," said Altidore.
"On and off the ball and linking up with the players around me, I just got better. It's that simple. I've become a much more confident player since then.
"The two leagues are completely different, but we're trying to play football which looks good and hopefully I can score some goals."
Altidore also scored in four consecutive internationals for the United States in June.